Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 26 May 2020 16:00:28 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Greentime Hu <greentime.hu@sifive.com>
Cc:     guoren@linux.alibaba.com, vincent.chen@sifive.com,
        paul.walmsley@sifive.com, palmerdabbelt@google.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v4 01/13] ptrace: Use regset_size() for dynamic
 regset size.
Message-ID: <20200526140027.GC24212@redhat.com>
References: <cover.1590474856.git.greentime.hu@sifive.com>
 <3700190a602a6d30fcbf76e1eea667e29a65c4c9.1590474856.git.greentime.hu@sifive.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <3700190a602a6d30fcbf76e1eea667e29a65c4c9.1590474856.git.greentime.hu@sifive.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 05/26, Greentime Hu wrote:
>
> @@ -882,13 +882,18 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
>  	const struct user_regset_view *view = task_user_regset_view(task);
>  	const struct user_regset *regset = find_regset(view, type);
>  	int regset_no;
> +	unsigned int size;
>
> -	if (!regset || (kiov->iov_len % regset->size) != 0)
> +	if (!regset)
>  		return -EINVAL;
>
>  	regset_no = regset - view->regsets;
> -	kiov->iov_len = min(kiov->iov_len,
> -			    (__kernel_size_t) (regset->n * regset->size));
> +	size = regset_size(task, regset);
> +
> +	if ((kiov->iov_len % size) != 0)
> +		return -EINVAL;

Hmm. this doesn't look right.

Before this patch we check "iov_len % regset->size", this is not the same
as "iov_len % regset_size()".

IOW, currently you can read/write, say, only the 1st register, you patch
breaks this?

Oleg.